Solar Influences
On
Global Change

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Solar Influences On Global Change Board on Global Change Commission on Geosciences, Environment, and Resources National Research Council National Academy Press Washington, D.C. 1994 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the ad hoc group responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. This work was sponsored by the National Science Foundation, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, United States Geological Survey, United States Department of Agriculture, Office of Naval Research, and Department of Energy under Contract No. OCE 9313563. Library of Congress Catalog Card No. 94-67788 International Standard Book Number 0-309-05148-7 Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, N.W. Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan Area) B-468 Cover artist, Marilyn Marshall Kirkman finds her artistic inspiration in the  Rocky Mountain West. Born in Wyoming and now living in Colorado, she is  surrounded by a world that demands expression. Vivid color and strong values,  eliciting light, convey her message. Marilyn Kirkman attended Mills College and is a graduate of the University of  Wyoming. Having been a teacher and parent, she is now a freelance artist.  Largely self-taught, she specializes in watercolor painting. Her work is  represented by the Arati Artists Gallery, Colorado Springs, CO. Copyright 1994 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the ad hoc group responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. This work was sponsored by the National Science Foundation, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, United States Geological Survey, United States Department of Agriculture, Office of Naval Research, and Department of Energy under Contract No. OCE 9313563. Library of Congress Catalog Card No. 94~7788 International Standard Book Number 0-309-05148-7 Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, N.W Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan Area) . B-468 Cover artist, Marilyn Marshall Kirkman finds her artistic inspiration in the Rocly Mountain West. Born in Wyoming and now living in Colorado, she is surrounded by a world that demands expression. Vivid color and strong values, eliciting light, convey her message. Marilyn Kirkman attended Mills College and is a graduate of the University of Wyoming. Having been a teacher and parent, she is now a freelance artist. Largely self-taught, she specializes in watercolor painting. Her work is represented by the Arati Artists Gallery, Colorado Springs, CO. Copyright 1994 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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Page iii BOARD ON GLOBAL CHANGE EDWARD A. FRIEMAN, Scripps Institution of Oceanography, Chairman ERIC J. BARRON, Pennsylvania State University ROBERT COSTANZA, Maryland Institute for Ecological Economics JEFF DOZIER, University of California PETER EAGLESON, Massachusetts Institute of Technology PRISCILLA C. GREW, Minnesota Geological Survey RICHARD E. HALLGREN, American Meteorological Society ESTELLA LEOPOLD, University of Washington PAMELA A. MATSON, NASA-Ames Research Center VEERABHADRAN RAMANATHAN, University of California, San Diego VERNON W. RUTTAN, University of Minnesota ROBERT H. SOCOLOW, Princeton University KARL K. TUREKIAN, Yale University GUNTER WELLER, University of Alaska Ex-Officio Members (U.S. Members, ICSU Scientific Committee for the International Geosphere-Biosphere Program (IGBP)) JAMES J. McCARTHY, Harvard University JERRY M. MELILLO, The Ecosystem Center S. ICHTIAQUE RASOOL, University of Paris VI (U.S. Members, Joint Scientific Committee for the World Climate Research Program (WCRP)) MARGARET S. LEINEN, University of Rhode Island JERRY D. MAHLMAN, National Oceanic and Atmospheric Administration (U.S. Member, International Steering Committee for the Human Dimensions of Global Change Program) HAROLD K. JACOBSON, University of Michigan Staff JOHN S. PERRY, Staff Director CLAUDETTE BAYLOR-FLEMING, Administrative Assistant DONALD H. HUNT, Consultant

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Page iv COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES M. GORDON WOLMAN, The Johns Hopkins University, Baltimore, MD, Chairman PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh, PA EDITH BROWN WEISS, Georgetown University Law Center, Washington, DC PETER S. EAGLESON, Massachusetts Institute of Technology, Cambridge, MA EDWARD A. FRIEMAN, Scripps Institution of Oceanography, La Jolla, CA W. BARCLAY KAMB, California Institute of Technology, Pasadena, CA JACK E. OLIVER, Cornell University, Ithaca, NY FRANK L. PARKER, Vanderbilt/Clemson University, Nashville, TN RAYMOND A. PRICE, Queen's University at Kingston, Ontario, Canada THOMAS A. SCHELLING, University of Maryland, College Park, MD LARRY L. SMARR, University of Illinois, Urbana-Champaign, IL STEVEN M. STANLEY, The Johns Hopkins University, Baltimore, MD VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, FL WARREN WASHINGTON, National Center for Atmospheric Research, Boulder, CO Staff STEPHEN RATTIEN, Executive Director STEPHEN D. PARKER, Associate Executive Director MORGAN GOPNIK, Assistant Executive Director JEANETTE SPOON, Administrative Officer SANDI FITZPATRICK, Administrative Associate ROBIN ALLEN, Senior Project Assistant (BOND)

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Page v Acknowledgments The Board is deeply indebted to the following group of scientists for their contributions to this report: JUDITH LEAN, Naval Research Laboratory, Group Chair DANIEL BAKER, University of Colorado MARVIN GELLER, SUNY at Stony Brook THOMAS POTEMRA, The Johns Hopkins University GEORGE REID, National Oceanic and Atmospheric Administration DAVID RIND, National Aeronautics and Space Administration RAYMOND ROBLE, National Center for Atmospheric Research ORAN WHITE, National Center for Atmospheric Research DONALD WILLIAMS, The Johns Hopkins University RICHARD WILLSON, Jet Propulsion Laboratory GEORGE WITHBROE, National Aeronautics and Space Administration DONALD WUEBBLES, Lawrence Livermore National Laboratory

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Page vi The National Academy of Sciences is private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. Robert M. White are chairman and vice-chairman, respectively, of the National Research Council.

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Page vii Preface In a series of reports over the past decade, the National Research Council (NRC) has outlined a broad scientific agenda to advance our understanding of the processes of global change. These studies stimulated and nourished the evolution of international efforts centered on the International Geosphere-Biosphere Program (IGBP) and the World Climate Research Program and in our own country supported the development of the U.S. Global Change Research Program. As these programs move rapidly from concept to implementation, the NRC Board on Global Change (BGC) has continued to assess critically the scientific needs. Is the scientific agenda truly comprehensive? Are the priorities appropriate in terms of needs for understanding, scientific opportunities, and technological possibilities? Are there gaps that should be and could be filled? Can recommendations be usefully sharpened and focused? To address such questions, our Board organized extended ad hoc consultations in a few selected problem areas with informal groups of experts from the scientific community. We focused on problems that were fundamentally important to the program's goals, but were not yet being effectively addressed within the program. Solar influences on the Earth system clearly constituted one such issue. The Sun's energy makes life on this planet possible. Interactions between solar energy and the radiative properties of the atmosphere maintain an equable climate through the greenhouse effect, and there is much concern about human-induced changes in the atmosphere. But the Sun itself is known to vary significantly

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Page viii in its activity. What are the implications of these changes for an already changing planet? These considerations led the planners of the USGCRP to include solar influences as a major element of the science program. However, the research agenda was at the time relatively undeveloped. What specific research initiatives could be proposed to fill this gap and to improve understanding of the role of the Sun in global change? In 1990, our Board requested the assistance of a talented group of active research scientists led Dr. Judith Lean of the Naval Research Laboratory to address these issues. Her group was asked to assist in developing a brief report identifying those aspects of research on the Sun and its interactions with our planet that would contribute to an understanding of global change, together with scientific approaches to developing research plans. It was hoped that these ideas would be useful to the federal agencies as they formulated plans for the U.S. Global Change Research Program. We are very grateful to Dr. Lean and her collaborators for working with us to develop a set of specific foci for research in this central problem area. We also wish to thank the following individuals: Dr. Jack Eddy provided the inspiration for this report. The indication that the Sun may be important for the Earth is his vision, carried through the past two decades. His initial concepts, carefully documented in the 1982 Academy Report on Solar Variability, Weather and Climate, laid the groundwork for this more recent assessment of the relationship. Donald Williams and members of NRC's Committee on Solar Terrestrial Research (CSTR), which together with the Board on Global Change sponsored the ad hoc Group on Solar Influences on Global Change, provided useful critical comments on a draft of the report. Valuable comments were also provided by many members of the solar and terrestrial research communities, including Linwood Callis, Gizella Dreschoff, Rolando Garcia, John Harvey, James Hecht, Thomas Holzer, Lon Hood, Charles Jackman, Robert Meier, Brian Tinsley, and Edward Zeller. Gary Rottman provided preliminary SOLSTICE data.

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Page ix We also appreciate the work of Dr. John S. Perry, Mr. Donald Hunt, and Ms. Claudette Baylor-Fleming of the NRC staff in supporting this effort. Edward A. Frieman, Chairman Board on Global Change

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Page xi Contents EXECUTIVE SUMMARY 1 Scientific Conclusions 2 Recommendations 10 1 INTRODUCTION 13 The Coupled Sun-Earth System 13 Global Change Research 20 Solar Influences on Global Change: A Major Scientific Research Element of the USGCRP 21 Objectives of the Report 22 2 SOLAR VARIATIONS AND CLIMATE CHANGE 23 Background 23 Total Solar Irradiance Variability 26 Contemporary measurements 26 Implications from observations of solar surrogates 29 Geophysical proxies 31 Evidence from observations of Sun-like stars 32 Solar Forcing of Climate Change 33 Solar irradiance changes and the relatively recent climate 36

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Page xii Solar activity cycles and the weather 40 Insolation changes due to orbital variations 44 3 SOLAR VARIATIONS, OZONE, AND THE MIDDLE ATMOSPHERE 49 Background 49 Solar Ultraviolet Radiation 53 Measurements of solar UV spectral irradiance 53 Irradiance variability parameterizations 56 Energetic Particles 58 Solar proton events 58 Relativistic electrons 61 Galactic cosmic rays 65 Solar Forcing of the Middle Atmosphere 66 Effects from variations in UV irradiance 66 Effects from solar proton events 68 Effects from relativistic electron precipitation 69 Ultraviolet Radiation Reaching the Biosphere 70 4 SOLAR VARIATIONS AND THE UPPER ATMOSPHERE 73 Background 73 Solar EUV and UV Radiation 74 Measurements of solar EUV spectral irradiance 74 Irradiance variability parameterizations 76 Auroral Particle and Electric Field Inputs 78 Global Currents and Electric Field Couplings 81 Global circuit processes 81 Electric couplings between the upper and lower atmospheres 83 Solar Forcing and Global Change within the Upper Atmosphere 84 Couplings of the Upper Atmosphere to the Lower Atmosphere 85

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Page xiii 5 SOLAR VARIATIONS AND EARTH'S NEAR-SPACE ENVIRONMENT 89 Background 89 The Solar Wind and the Earth's Magnetosphere 90 Solar Eruptive Events and Geomagnetic Storms 91 Terrestial Impacts 93 6 UNDERSTANDING THE VARIABLE SUN 95 Background 95 Origins of Solar Variability 96 Relationship between Solar Surface Structure and Energy from the Sun-as-a-Star 100 Radiation 100 Plasma and particles 106 Cosmic rays 107 Requirements for Improved Understanding 107 Present 107 Past 109 Future 110 7 RESEARCH STRATEGIES 111 Monitoring Solar Forcing 112 Total solar irradiance 113 Solar spectral irradiance 114 Energetic particles 116 Ground based solar variability indicators 117 Monitoring Terrestrial Solar Effects 119 Lower atmosphere 119 Middle atmosphere 120 Upper atmosphere 121 Understanding Solar Influences on Global Change 122 Studies of present day behavior 123 Records of the past 125 Understanding and Predicting Solar Variability 126 Programmatic Approach 129 Need for interdisciplinary efforts 129 Connections to other areas of the USGCRP 130

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Page xiv Agency roles 130 International aspects 133 8 RECOMMENDATIONS 135 Scientific Rationale for Assigning Priorities 135 Recommendations 135 Primary recommendations 135 Additional recommendations 136 REFERENCES 141 ACRONYMS 161 Solar Influences On Global Change

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SOLAR INFLUENCES ON GLOBAL CHANGE

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